I've actually been looking a lot into this lately as I have a very dear friend with Parkinsons. It turns out there are similarities between Alzheimer's and Parkinsons and both are linked with environmental toxins causing damage. The last year I've spent researching and have run into some amazing research papers and discoveries around carbon 60 (C60) and it's ability to slow down and in some cases reverse Alzheimer's and other neurological damage.
In order to make this affordable for my friend and others I work with I ended up building a lab and am now producing C60 Oils. www.C60Solutions.com (under construction-will be finished soon!)
There are numerous research papers linked on the RESEARCH page which might help you also. One which is not on it yet but will be soon is : Effects of Carbon Nanoparticles on the Aggregation of Alzheimers Beta-Amyloid Peptide (You may have to request the full research paper to see it or sign in with your University credentials) but it's well worth the read. I hope to have it up on the site soon. Do see the first one linked: 'A carboxyfullerene SOD mimetic improves cognition and extends the lifespan of mice'. Cognition and memory were enhanced.

When I find it I'm going to link a PhD who had Alzheimer's and experimented with C60's on himself in the early stage to try and stop it and had incredible success reversing it completely using C60's in Olive Oil.

So there is hope!

Looking at this from a Spiritual view point there is no cause for concern, what is being experienced is happening to the body/Mind only not the Spirit of your loved one, when the Spirit of your loved one sheds their Body there will be no impairment from the Alzheimer's the body/mind experienced.
In other words the Alzheimer's will only last (unless cured!) for as long as there is a body/mind.
So please be at ease, it happened on Earth and stays on earth and will not cross over with them. :)